Methods for treating metal sheets in order to produce sheet metal parts with locally modified properties, particularly greater strengths, are generally known.
Sheet metal parts with locally greater strengths can be produced by increasing the material thickness. DE 10 2006 034 620 A1 describes a method for manufacturing sheet metal parts, in which a reinforcement is applied onto an area of a substructure by means of laser welding. Since no pressure can be exerted upon the welding point during the laser welding operation, the quality of the weld significantly depends on how soft the reinforcement becomes under the influence of the laser beam and how intimately it thereby adapts to the substructure. The quality of the laser beam therefore significantly influences the welding results. The different mechanical properties in the reinforced and in the unreinforced areas of the metal sheets lead to high tensions when the welding seams and the adjacent heat-affected zone are subjected to loads. This may cause the metal sheet to tear open in or adjacent to the welded joint.
After the reinforcement has been welded on, the overall thickness of the metal sheet is greater in the area of the reinforcement than in the unreinforced area. This conventional metal sheet is not suitable for applications, in which a uniform thickness is required over the entire metal sheet. It is particularly unsuitable for deep-drawing because the abrupt differences in thickness in the metal sheet can only be insufficiently considered in the deep-drawing tool.
DE 6 940 1390 T2 discloses an aluminum sheet, on which a perforated sheet or a grating of steel is fastened by means of cold forming in order to create a structural component, the mechanical strength of which is greater than that of just the aluminum sheet.
The intimate connection between steel and aluminum in this conventional structural component significantly complicates recycling. The structural component has a strong tendency to contact corrosion and therefore requires, in contrast to the original aluminum sheet, effective corrosion protection on its surface. However, if a paint layer is conventionally applied onto the structural component as corrosion protection, the different coefficients of thermal expansion of aluminum and steel promote the separation of this corrosion protection layer precisely at the boundaries between the materials.
Another problem in the further processing of this known structural component can be seen in that connecting techniques suitable for aluminum are frequently incompatible with a steel surface and vice versa; in particular, different operating parameters are required for welding aluminum than for welding steel. If another component should be welded onto the structural component, it therefore must be known beforehand whether it should be welded to a steel surface or an aluminum surface, wherein welding seams extending over both types of surfaces cannot be produced. Repair work is particularly difficult under this conditions.